描述
Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen.
Example 1:
Input
["Solution", "getRandom", "getRandom", "getRandom", "getRandom", "getRandom"]
[[[1, 2, 3]], [], [], [], [], []]
Output
[null, 1, 3, 2, 2, 3]
Explanation
Solution solution = new Solution([1, 2, 3]);
solution.getRandom(); // return 1
solution.getRandom(); // return 3
solution.getRandom(); // return 2
solution.getRandom(); // return 2
solution.getRandom(); // return 3
// getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning.
Note:
The number of nodes in the linked list will be in the range [1, 104]
-104 <= Node.val <= 104
At most 104 calls will be made to getRandom.
解析
根据题意，只需要将链表中的所有 val 都放入列表 l 中，然后随机从里面取出一个值即可。
解答
class Solution(object):
def __init__(self, head):
"""
@param head The linked list's head.
Note that the head is guaranteed to be not null, so it contains at least one node.
:type head: ListNode
"""
self.l = []
if head:
self.l.append(head.val)
while head.next is not None:
self.l.append(head.next.val)
head = head.next
def getRandom(self):
"""
Returns a random node's value.
:rtype: int
"""
return random.choice(self.l)
运行结果
Runtime: 52 ms, faster than 96.63% of Python online submissions for Linked List Random Node.
Memory Usage: 17.8 MB, less than 9.12% of Python online submissions for Linked List Random Node.
原题链接：leetcode.com/problems/li…
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